References of "Carnat, Gauthier"
     in
Bookmark and Share    
See detailN2O dynamics in sea ice, insights from a first time series and isotopic tools
Kotovitch, Marie ULg; Tison, Jean-Louis; Fripiat, François et al

Conference (2017, March 25)

Nitrous oxide (N2O) is a potent greenhouse gases that has a lifetime of 114 years in the atmosphere and a global warming potential 300 time higher than that of CO2. However there are still large ... [more ▼]

Nitrous oxide (N2O) is a potent greenhouse gases that has a lifetime of 114 years in the atmosphere and a global warming potential 300 time higher than that of CO2. However there are still large uncertainties and gaps in the understanding of the N2O cycle in polar oceans and particularly associated to sea ice. Sources and sinks of N2O are therefore poorly quantified. To date, only one study by Randall et al. 2012 present N2O measurements in sea ice. They pointed out that sea ice formation and melt has the potential to generate sea-air or air-sea fluxes of N2O, respectively. The main processes (except the transport processes) involved in the N2O cycle within the aquatic environment are nitrification and denitrification. Recent observations of significant nitrification in Antarctic sea ice shed a new light on nitrogen cycle within sea ice. It has been suggested that nitrification supplies up to 70% of nitrate assimilated within Antarctic spring sea ice. Corollary, production of N2O, a by-product of nitrification, can potentially be significant. Our recent studies in Antarctic land fast ice in McMurdo Sound, confirmed this suggestion, where N2O release to the atmosphere was estimated to reach 4 µmol.m-2.yr-1. But this assessment is probably an underestimation since it only accounts for dissolved N2O while a significant amount of N2O is likely to occur in the gaseous form like N2, O2 and Ar. We will then address the new tools to measure the bulk concentration of N2O (dissolved and gaseous) in sea ice, and the production of N2O by sympagic microorganisms - what process is dominant and how much N2O is produced - based on the first time series of N2O measurement in sea ice. The determination of the isotopic composition of N2O using cavity enhanced laser absorption spectroscopy technique (Off-axis ICOS) will allow us to determine the origin of these processes. [less ▲]

Detailed reference viewed: 16 (2 ULg)
Full Text
Peer Reviewed
See detailInfluence of short-term synoptic events and snow depth on DMS, DMSP, and DMSO dynamics in Antarctic spring sea ice
Carnat, Gauthier; Brabant, Frédéric; Dumont, Isabelle et al

in Elementa: Science of the Anthropocene (2016), 4(0), 000135

Temporal changes in the concentration profiles of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO) were measured in pack ice from the Bellingshausen Sea (Antarctica ... [more ▼]

Temporal changes in the concentration profiles of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), and dimethylsulfoxide (DMSO) were measured in pack ice from the Bellingshausen Sea (Antarctica) during the winter-spring transition of 2007. Two sites with contrasting snow and ice thicknesses were sampled, with high concentrations of DMS, DMSP, and DMSO observed at both sites, especially in surface ice. These high concentrations were shown to correspond to the development of a surface ice microalgal community dominated by strong DMSP producers (flagellates and dinoflagellates) following flooding of the ice cover. Several short-term synoptic events were observed and shown to influence strongly the dynamics of sea ice DMS, DMSP, and DMSO. In particular, a cold spell event was associated with drastic changes in the environmental conditions for the sea ice microbial communities and to a remarkable increase in the production of dimethylated sulfur compounds at both sites. A good correlation between all dimethylated sulfur compounds, sea ice temperature, and brine salinity suggested that the observed increase was triggered mainly by increased thermal and osmotic stresses on microalgal cells. Atmospheric forcing, by controlling sea ice temperature and hence the connectivity and instability of the brine network, was also shown to constrain the transfer of dimethylated sulfur compounds in the ice towards the ocean via brine drainage. Analysis of the two contrasting sampling sites shed light on the key role played by the snow cover in the sea ice DMS cycle. Thicker snow cover, by insulating the underlying sea ice, reduced the amplitude of environmental changes associated with the cold spell, leading to a weaker physiological response and DMS, DMSP, and DMSO production. Thicker snow also hampered the development of steep gradients in sea ice temperature and brine salinity, thereby decreasing the potential for the release of dimethylated sulfur compounds to the ocean via brine drainage. [less ▲]

Detailed reference viewed: 21 (2 ULg)
See detailAnnual dynamics of pCO2 within bulk sea ice and related CO2 fluxes at Cape Evans (Antarctica)
Van Der Linden, Fanny ULg; Champenois, Willy ULg; Heinesch, Bernard ULg et al

Poster (2016, February 12)

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice ... [more ▼]

Sea ice is a biome actively participating in the regional cycling of CO2 as both a source and a sink at different times of the year. In the frame of the YROSIAE project (Year-Round Ocean-Sea-Ice-Atmosphere Exchanges), annual dynamics of sea ice pCO2 was compared with CO2 fluxes measured by automated accumulation chambers at Cape Evans (Ross Island, Antarctica). Results confirmed a general trend of brine pCO2 supersaturation with respect to the atmosphere during the late winter (concentration of dissolved inorganic carbon - DIC - in brine and brine expulsion in the brine skim) leading to CO2 degassing, and undersaturation during the spring (carbon-uptake by autotrophs and brine dilution) leading to atmospheric CO2 uptake. Despite high primary production at the bottom of the ice in spring, DIC profiles suggest that sea ice as a whole appears to be net heterotrophic. Still, sea ice absorbs CO2 from the atmosphere, as a result of physical processes. Some variability in the CO2 fluxes (both in magnitude and sign) could not be explained by variability in sea ice pCO2 but rather seemed driven by variability in atmospheric conditions and sea ice surface properties. For instance, in late spring, CO2 fluxes showed a diurnal variability (from CO2 degassing to uptake) related to atmospheric temperature variations. Large and episodic CO2 fluxes were systematically positively correlated with strong wind events, and large CO2 degassing was observed over thin, wet and salty snow cover. [less ▲]

Detailed reference viewed: 55 (14 ULg)
Full Text
See detailYear Round Survey of Ocean-Sea Ice-Air Exchanges – the YROSIAE survey
Delille, Bruno ULg; Van Der Linden, Fanny ULg; Fripiat, François et al

Poster (2015, September 08)

YROSIAE survey aimed to carry out a year-round integrated survey of land-fast sea ice focusing on the study of sea ice physics and biogeochemistry in order to a) better understand and budget exchanges of ... [more ▼]

YROSIAE survey aimed to carry out a year-round integrated survey of land-fast sea ice focusing on the study of sea ice physics and biogeochemistry in order to a) better understand and budget exchanges of energy and matter across the ocean-sea ice-atmosphere interfaces during sea ice growth and decay and b) quantify their potential impact on fluxes of climate gases (CO2, DMS, CH4, N2O) to the atmosphere and on carbon and macro- nutrients and micro-nutrients export to the ocean. We will present the aims, overall approach and integrated sampling strategy of the YROSIAE survey. We will also discuss CO2 and N2O dynamics within sea ice. It appears that sea ice acts as a source of CO2 for the atmosphere in winter, counterbalancing spring sink. In addition, mineralization in spring appears to alleviate spring CO2 uptake. Intense nitrification in sea ice in spring fosters emission of N2O at the air-ice interface. [less ▲]

Detailed reference viewed: 47 (5 ULg)
Full Text
Peer Reviewed
See detailFirst estimates of the contribution of CaCO3 precipitation to the release of CO2 to the atmosphere during young sea ice growth
Geilfus, Nicolas-Xavier ULg; Carnat, Gauthier; Dieckmann, G.S. et al

in Journal of Geophysical Research. Oceans (2013), 118(1-12), 244-255

We report measurements of pH, total alkalinity, air-ice CO2 fluxes (chamber method) and CaCO3 content of frost flowers (FF) and thin landfast sea ice. As the temperature decreases, concentration of ... [more ▼]

We report measurements of pH, total alkalinity, air-ice CO2 fluxes (chamber method) and CaCO3 content of frost flowers (FF) and thin landfast sea ice. As the temperature decreases, concentration of solutes in the brine skim (BS) increases. Along this gradual concentration process, some salts reach their solubility threshold and start precipitating. The precipitation of ikaite (CaCO3.6H2O) was confirmed in the FF and throughout the ice by Raman spectroscopy and X-ray analysis. The amount of ikaite precipitated was estimated to be 25 µmol kg-1 melted FF, in the FF and is shown to decrease from 19 µmol kg-1 to 15 µmol kg-1 melted ice in the upper part and at the bottom of the ice, respectively. CO2 release due to precipitation of CaCO3 is estimated to be 50 µmol kg-1 melted samples. The dissolved inorganic carbon (DIC) normalized to a salinity of 10 exhibits significant depletion in the upper layer of the ice and in the FF. This DIC loss is estimated to be 2069 µmol kg-1 melted sample and corresponds to a CO2 release from the ice to the atmosphere ranging from 20 to 40 mmol m-2 d-1. This estimate is consistent with flux measurements of air-ice CO2 exchange. Our measurements confirm previous laboratory findings that growing young sea ice acts as a source of CO2 to the atmosphere. CaCO3 precipitation during early ice growth appears to promote the release of CO2 to the atmosphere however its contribution to the overall release by newly formed ice is most likely minor. [less ▲]

Detailed reference viewed: 35 (1 ULg)
Full Text
Peer Reviewed
See detailInvestigations on physical and textural properties of Arctic first-year sea ice in the Amundsen Gulf, Canada, November 2007–June 2008 (IPY-CFL system study)
Carnat, Gauthier; Papakyriakou, Timothy; Geilfus, Nicolas-Xavier ULg et al

in Journal of Glaciology (2013), 59(217),

We report sea-ice temperature and bulk salinity measurements as well as textural analysis from 33 first-year drift- and fast-ice stations sampled between November 2007 and June 2008 in the southern ... [more ▼]

We report sea-ice temperature and bulk salinity measurements as well as textural analysis from 33 first-year drift- and fast-ice stations sampled between November 2007 and June 2008 in the southern Beaufort Sea–Amundsen Gulf, Canadian Arctic, during the International Polar Year Circumpolar Flaw Lead (IPY-CFL) system study. We use this significant dataset to investigate the halothermodynamic evolution of sea ice from growth to melt. A strong desalination phase is observed over a small time window in the spring. Using calculated proxies of sea-ice permeability (brine volume fraction) and of the intensity of brine convection (Rayleigh number) we demonstrate that this phase corresponds to full-depth gravity drainage initiated by a restored connectivity of the brine network with warming in the spring. Most stations had a textural sequence typical of Arctic first-year ice, with granular ice overlying columnar ice. Unusual textural features were observed sporadically: sandwiched granular ice, platelet ice and draped platelet ice. We suggest that turbulence in leads and double diffusion in strong brine plumes following the refreeze of cracks are plausible mechanisms for the formation of these textures. [less ▲]

Detailed reference viewed: 25 (1 ULg)
See detailFluxes of dimethylsulfide from warming sea ice
Carnat, Gauthier; Zhou, Jiayun; Papakyriakou, Tim et al

Poster (2012, May)

Detailed reference viewed: 25 (1 ULg)
Full Text
See detailO2/Ar and CH4 measurements in sea ice : clues for the key status of sea ice in the climate system
Zhou, Jiayun; Tison, Jean-Louis; Eicken, Hajo et al

in Geophysical Research Abstracts (2011, April 08), 13

Detailed reference viewed: 29 (7 ULg)
Full Text
See detailTemporal evolution of biogeochemical properties of landfast sea ice at Barrow (Alaska)
Zhou, Jiayun ULg; Tison, Jean-Louis; Eicken, Hajo et al

Poster (2011, March)

Detailed reference viewed: 25 (3 ULg)
See detailA multidisciplinary approach to understanding the sea ice system: implications on gas. Gordon Research Seminars
Zhou, Jiayun ULg; Tison, Jean-Louis; Eicken, Hajo et al

Conference (2011, March)

Detailed reference viewed: 13 (1 ULg)
Full Text
See detailDynamic processes in sea ice captured by the temporal evolution of its biogeochemical
Zhou, Jiayun; Tison, Jean-Louis; Eicken, Hajo et al

in VLIZ Special Publication (2011), 48

Detailed reference viewed: 17 (4 ULg)
See detailAir-ice CO2 fluxes and pCO2 dynamics in sea ice in the Arctic coastal area (Amundsen Gulf, Canada)
Geilfus, Nicolas-Xavier ULg; Tison, Jean Louis; Carnat, Gauthier et al

Conference (2010, May)

Detailed reference viewed: 25 (5 ULg)
Full Text
See detailAir-sea ice CO2 fluxes measurement with eddy-covariance micrometeorological technique
Heinesch, Bernard ULg; Aubinet, Marc ULg; Carnat, Gauthier et al

Conference (2010, April)

Detailed reference viewed: 47 (8 ULg)
Full Text
See detailMicrometeorological survey of air-sea ice CO2 fluxes in arctic coastal waters
Heinesch, Bernard ULg; Tison, Jean-Louis; Carnat, Gauthier et al

in Geophysical Research Abstracts (2010), 12(EGU2010-10570),

Detailed reference viewed: 29 (11 ULg)
See detailpCO2 in sea ice and CO2 fluxes estimates: where do we stand today?
Tison, J.; Delille, Bruno ULg; Papakyriakou, T. N. et al

Conference (2009, December)

Detailed reference viewed: 4 (0 ULg)
See detailSpatiotemporal variations of DMSO in arctic sea ice: new insights using dmso reductase enzyme
Carnat, Gauthier; Brabant, Frederic; Papakyriakou, Tim et al

Poster (2009, November)

Detailed reference viewed: 35 (4 ULg)
Full Text
See detailAir-ice CO2 fluxes and pCO2 dynamics in sea ice in the Arctic (Amundsen Gulf)
Geilfus, Nicolas-Xavier ULg; Tison, Jean Louis; Carnat, Gauthier et al

Conference (2009, November)

Detailed reference viewed: 15 (5 ULg)
See detailAir-ice CO2 fluxes in the Arctic coastal area
Geilfus, Nicolas-Xavier ULg; Tison, Jean Louis; Carnat, Gauthier et al

Poster (2009, May)

Detailed reference viewed: 79 (4 ULg)
Full Text
See detailAir-ice CO2 fluxes in the Arctic coastal area (Amundsen Gulf)
Geilfus, Nicolas-Xavier ULg; Tison, Jean Louis; Carnat, Gauthier et al

Poster (2009, March)

Detailed reference viewed: 16 (1 ULg)
See detailDynamics of flood-freeze cycles during the SIMBA experiment (Brussels and Liège Stations - Bellingshaussen Sea, Antarctica)
Tison, Jean Louis; Brabant, Frederic; Geilfus, Nicolas-Xavier ULg et al

Poster (2009, March)

Detailed reference viewed: 23 (1 ULg)